Probiotic bacteria are selected for their health-promoting properties. As probiotics exert their benefit as living organism (Guarner, F. and G. J. Schaafsma. 1998. “Probiotics”. Int. J. Food Microbiol. 39:237-238), the bacteria should survive the gastro-intestinal track conditions. In industrial application, large-scale production requires the additional ability of the probiotics to tolerate food processing and storage. These production steps are characterized by different stresses compromising the good survival of the bacteria. Amongst them, high or low temperature, high osmotic pressure, oxidation, and humidity are likely key factors.
Some species of probiotic bacteria are in particular known to have a poor temperature, oxygen, or spray-drying tolerance. Prominent examples of such probiotics with a poor stress tolerance are, e.g., Bifidobacteria, in particular Bifidobacterium longum (Simpson, P. J., C. Stanton, G. F. Fitzgerald, and R. P. Ross. 2005. “Intrinsic tolerance of Bifidobacterium species to heat and oxygen and survival following spray drying and storage”. J. Appl. Microbiol. 99:493-501).
To address this problem and to increase the survival rate of probiotics during food production, several approaches are presently used, including microencapsulation, addition of protective agents, oxygen-impermeable packaging, and improvement of the growth or processing conditions.
However, these approaches are complex and laborious to carry out and often require the addition of further compounds that may have side effects and that may be unwanted in the final food-product.
On the other hand there are applications where it is desired to have as few living bacteria in a product as possible. Presently, such sterile products are prepared by applying intense heat and/or pressure. In this case it would be desirable to have probiotics available that can effectively be inactivated even without the need for high energy treatments.